Examples of rotational force generating means include a motor, a prime mover, and a battery. These rotational force generation means have found their applications in various industrial fields.
In order to operate the rotational force generating means described above, electricity, or a liquid fuel, or a solid fuel is required. Therefore, the use of such a rotational force generating means is restricted in a situation where supply of electricity or fuel is difficult.
In order to solve such a problem with the rotational force generating means described above, Korean Utility Model Registration No. 199047 discloses a “Rotary Force Generator Using Spiral spring” (hereinafter, referred to as “conventional clock spring-based rotary force generator”).
FIG. 11 is a cross-sectional view illustrating a process in which the conventional clock spring-based rotary force generator 100 generates a rotational force, and FIG. 12 is a perspective view viewed from a direction of A-A line of FIG. 11.
The conventional clock spring-based rotary force generator will be described below. Reference numerals 101, 102, and 103 respectively denote first, second, and third diaphragms fastened by fastening means 104 in a manner of being arranged in parallel at predetermined intervals.
An input shaft 105 is coupled with and is installed to pass through the first, second and third diaphragms 101, 102 and 103 in a rotatable manner. One end portion of the input shaft 105 protrudes outward from an outer surface of the first diaphragm 101 and a leading end surface of the end portion is a flat surface serving as a rotary means coupling portion 105a. 
A spiral spring 106 is spirally wound around a portion of the input shaft 105 disposed between the first diaphragm 101 and the second diaphragm 102. An inner end of the reel sparing 106 is fixed to the outer circumferential surface of the input shaft 105 and an outer end of the reel sparing 106 is fixed to one of the fastening means 104 that respectively fasten the first diaphragm 101 and the second diaphragm 102.
A main drive gear 107 is slidably coupled with a portion of the input shaft 105 between the second diaphragm 102 and the third diaphragm 103 and a ratchet wheel 108 is fixed to one side of the main drive gear 107.
A rotary plate 109 is fixed to a portion of the input shaft 105 at a position close to the ratchet wheel 108, and an outer end of a stopper plate 110 is fixed to the rotary plate 109. An inner end of the stopper plate 110 is resiliently inserted into a space (valley) between the teeth (ridges) of the ratchet wheel 108.
In the case of the configuration described above, in a state where the input shaft 105 is rotated in the counterclockwise direction (i.e., to the left side), the inner end of the stopper plate 110 slides out of the space between the teeth of the ratchet wheel 108 and thus the turning force of the input shaft 105 is not transmitted to the main drive gear 107. Conversely, in a state where the input shaft 105 is rotated in the clockwise direction, the inner end of the ratchet wheel 108 is locked in the space between the teeth of the ratchet wheel 108 and thus the turning force of the input shaft 105 can be transmitted to the main drive gear 107.
The rotational force of the main drive gear 107 is doubled by first and second speed gears 111 and 112, and the doubled rotational force can be output via an output shaft 112a that is installed to rotatably fasten the second speed gear 112. On the other hand, the rotation speed of the output shaft 112a is controlled to be constant by a rotation speed control means 113.
The rotation speed control means 113 includes a speed gear 113a meshed with the second speed gear 112, a ratchet wheel 113b rotated by the speed gear 113a, a pendulum plate 113c rotatably mounted in the vicinity of the ratchet wheel 113b, and a pair of stopper pins 113d fixed to the pendulum plate 113c and inserted into each of the valleys of the ratchet wheel 113b, sequentially.
The rotation speed control means 113 controls the rotation speed of the output shaft 112a to be constant in such a manner that the pair of stopper pins 113d sequentially slide along the tooth surface of each tooth to enter the next valley of the ratchet wheel 113b that rotates in conjunction with the output shaft 112a for every tooth of the ratchet wheel 113b one after another.
In the case of generating a rotational force with the conventional clock spring-based rotary force generator, the input shaft 105 is rotated counterclockwise in a state where a rotary shaft (not illustrated) is coupled with the rotary means coupling portion 105a of the input shaft 105.
During the rotation of the input shaft 105, the rotational force of the input shaft 110 is not transmitted to the main drive gear 107 because the inner end of the stopper plate 110 is in the middle of sliding along the tooth surface of the ratchet wheel 108. Due to the rotation of the input shaft 105, the spiral spring 106 is wound around the input shaft 105 so that the elastic rotational force is accumulated.
In a state in which an external force is not applied to the input shaft 105 during the rotation of the input shaft 105, since the inner end of the stopper plate 110 is locked by the teeth of the ratchet wheel 108, there is no possibility that the input shaft 105 is rotated in the reverse direction by the elastic force of the spiral spring 106.
When the external force applied to the input shaft 105 is removed after the input shaft 105 is rotated by a rotary means by a predetermined number of revolutions as described above, the input shaft 105 is rotated in the reverse direction in conjunction with the main drive gear 107 by the elastic rotational force accumulated in the spiral spring 106 because the inner end of the stopper plate 110 is locked by the teeth of the ratchet wheel 108. Therefore, the rotational force of the main drive gear 107 is increased while being transmitted via the first and second speed gears 111 and 112 and thus the increased rotational force is output via the output shaft 112a. 
Accordingly, the conventional clock spring-based rotary force generator 100 is widely used because it can generate rotational force for a considerable period of time even under a condition where supply of fuel or electricity is difficult.
However, the conventional clock spring-based rotary force generator 100 has a problem that the rotation speed (revolutions per minute (RPM)) of the output shaft cannot be adjusted.
The clock spring-based rotary force generator 100 has another problem that, in the second half period of a full operation span of the output shaft, the unwinding rotational force decreases due to the inherent nature of a spiral spring and thus the rotational force of the output shaft decreases, resulting in the output shaft rotating slowly or even stopping.